The reaction of six Flourescein-conjugated lectins with human trophoblast and foetal limb are described. The trophoblast had marked membrane fluorescence after treatment with wheatgerm and Lotus tetragonolobus lectins. Concanavalin A reacted strongly with the trophoblastic cytoplasm but did not react with the nuclei. Most of the lectins had only weak reactions with foetal tissue, apart from the cartilage matrix which fluoresced strongly after treatment with several of the lectins. In addition, concanavalin A reacted with amylase-labile material, probably glycogen, in the skin epidermis and chondrocyte cytoplasm. Various substances were tested in order to determine the nature of the wheatgerm lectin receptor of trophoblast. Several secretory and binding proteins were found not to be responsible, and the identity of the receptor remains unknown.